1. Noise Control for Internal Combustion Engine Exhaust
Brad Fiedler
Chris VanWagenen
Greg Wodzicki
Kyle Desrosiers
Design Review – Week 5

2. Agenda Introduction / Background
Understanding the Problem and Current Technology
Courses of Action
Course of Action Comparison
Best Courses of Action
Closing
Questions

3. Introduction/Background
Customer Needs
Design Objectives
Risk Assessment
Gantt Chart

4. FSAE Formula One Vehicle
What year Vehicle is this?

5. Problem Background FSAE rules dictate engine noise under 110dB.
Glass pack
Exhaust
>110dB
FSAE rules dictate engine noise under 110dB.
Current Passive Noise Control device (Glass pack) holds engine sound from wide range above and below 110dB
Current technology is not tuned for optimal noise reduction or engine performance
Introduction / Background

6. Active / Passive Noise Cancellation
Design Objectives
Noise
Engine
Active / Passive Noise Cancellation
Exhaust
<110dB
Utilize Active / Passive Noise Cancellation Technology to:
Maintain engine output under FSAE limit of 110dB.
Adhere to all FSAE Rules
To not add significant weight to vehicle
Maintain/Improve engine performance
Lower Vehicle Center of Gravity
Introduction / Background

7. Performance Objective
Possible Performance Effects of Different Exhaust Technology:
A – No Exhaust Tuning
B – Traditional Exhaust Length Tuning
C – Possible Active Noise Cancellation Improvement*
* Dependent on cancellation method
Introduction / Background

8. Risk Assesment
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Introduction / Background

9. Project Plan
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Introduction / Background

10. Understanding the Problem and Current Technology
Internal Combustion Engine
ICE Exhaust Acoustics
Tuning a Exhaust
Understanding ANC
Lawnmower Engine
Glass Pack Muffler
Turbo Muffler
Baffle Muffler

11. Understanding the 4 Stroke ICE
Noise
Engine
Exhaust
Understanding the Problem and Current Technology

12. Understanding Optimal Acoustics
Exhaust Stage
Noise
Exhaust
Pressure From Combustion
Vacuum
Noise
Top Dead Center
Pressure From Vacuum
Understanding the Problem and Current Technology

13. Calculating Tuned Exhaust Length
Noise
Engine
Exhaust
𝐿= 𝑘∗ 𝐸 𝑜 ∗ 𝑉 𝑠 𝑁
𝑁 = Crankshaft Speed in RPM
𝑘 = Constant
Understanding the Problem and Current Technology

14. Understanding Active Noise Cancellation - 1
Superposition
Harmonics
Not Complete
Understanding the Problem and Current Technology

15. Understanding Active Noise Cancellation - 2
𝐵 𝑒 𝑖𝑤𝑡−𝑖 𝑘(𝐿 𝑡 − 𝐿 1 )
Noise
Speakers
Engine
Exhaust
𝐿 𝑡
𝐿 1
𝐴 𝑒 𝑖𝑤𝑡−𝑖𝑘𝑥
𝐴 𝑒 𝑖𝑤𝑡−𝑖𝑘𝑥 + 𝐵 𝑒 𝑖𝑤𝑡−𝑖 𝑘(𝐿 𝑡 − 𝐿 1 ) =0
Noise reduction formula can be further detailed, but is dependent on many variable including the number of microphones and speakers being used in the system
Signal Equations:
Noise Reduction:
𝑁𝑜𝑖𝑠𝑒 𝑅𝑒𝑑𝑢𝑐𝑡𝑖𝑜𝑛= 𝑃 𝑤𝑖𝑡ℎ 𝐶𝑎𝑛𝑐𝑒𝑙𝑙𝑖𝑛𝑔 𝑃 𝑤𝑖𝑡ℎ𝑜𝑢𝑡 𝑐𝑎𝑛𝑐𝑒𝑙𝑙𝑎𝑡𝑖𝑜𝑛
𝐴 𝑒 𝑖𝑤𝑡−𝑖𝑘𝑥 + 𝐵 𝑒 𝑖𝑤𝑡−𝑖 𝑘(𝐿 𝑡 − 𝐿 1 ) =0
𝐴+ 𝐵 𝑒 𝑖 𝑘(𝐿 1 ) 𝑥= 𝐿 𝑡
Understanding the Problem and Current Technology

16. Glass Pack Exhaust Travels through Pipe with Perforated Holes
Noise
Engine
Exhaust
Glass pack
Inner Pipe
Housing
Sound Insulation
Exhaust Travels through Pipe with Perforated Holes
Sound Insulation Absorbs Sound
Minimal Back Pressure
Least Effective in Reducing Sound
Understanding the Problem and Current Technology

17. Turbo Muffler No Baffles Exhaust Forced to turn back and forth
Noise
Engine
Exhaust
Turbo Muffler
No Baffles
Exhaust Forced to turn back and forth
Increases Exhaust Length
Increased Back Pressure with each turn
Sound Insulation Absorbs Sound
Moderately Effective in Reducing Sound
Understanding the Problem and Current Technology

18. Baffle Muffler Reflects Exhaust Throughout Chamber
Noise
Engine
Exhaust
Baffle Muffler
Reflects Exhaust Throughout Chamber
Reflections Cancel each other
Most Back Pressure created
Greatest Sound Reduction
Understanding the Problem and Current Technology

19. Lawnmower Engine
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Introduction / Background

20. Courses of Action Noise Reduction Techniques Explored
Signal Processing for ANC

21. Internal ANC with Microphone and Feedback
Speaker
Noise
Engine
Exhaust
Speaker Signal
<110dB
About:
Internal Speaker and Microphone Exposed to Exhaust Heat and possible Corrosion from Exhaust.
Feedback allows correction from
Controller
Primary Microphone
Feedback Microphone
Courses of Action

22. Exhaust in Speaker Chamber
Primary Microphone
Engine
Noise
Exhaust
<110dB
Speaker
Speaker Signal
About:
Internal Speaker and Microphone Exposed to Exhaust Heat and possible Corrosion from Exhaust.
Feedback allows correction from
Feedback Microphone
Controller

23. Multiple Speaker with Error Microphone
Speakers
Noise
Engine
Exhaust
Speaker Signal
<110dB
About:
Internal Speaker and Microphone Exposed to Exhaust Heat and possible Corrosion from Exhaust.
Feedback allows correction from
Controller
Primary Microphone
Feedback Microphone
Courses of Action

24. Signal Generation: Digital Signal Processing
The core subsystems include:
DSP - performs system initialization and executes the adaptive signal processing algorithm.  
Memory - stores executing code and data/parameters.  
AGC - maximizes the ADC SNR and maintains the overall system dynamic range.  
Audio CODEC - the residual noise signals are converted o digital form by the ADC. The DAC generates the out put anti-noise signals.   
Power Conversion - converts the battery power to run various functional blocks.
Courses of Action

25. Filtering Technique 1: Filtered-X Least Mean Squared Filter
Courses of Action